I would advise people here to read 'The Sleepwalkers: How Europe Went to War in 1914'. It a wonderful book exploring the causes for WW1 and focusing on just that. I think the strongest part of the book is that it goes beyond reiterating the usual accepted causes (diplomatic isolation of Germany, push for war from the military circles) and explores the complexity of pre-war diplomacy without assuming inevitability of the war. I think this resulted into a more unbiased approach: instead of trying to explain what caused the war postfactum, the author instead tries to adopt the political outlook of the contemporary politicians which really helps with understanding why certain actions were made and why they made sense politically - like Austria-Hungarian ultimatum.